1. Field of the Invention
The present invention relates to a light-blocking shutter in a fiber-optic connector or adapter that prevents light emissions from the fiber-optics of the connector when the adapter is open (i.e., when no mating connector is inserted). This prevents eye damage if a person should look into the open end of the connector that is carrying an optical signal. More specifically, the invention relates to light-blocking shutters in fiber-optic adapters that automatically block the opening through which the light signal is transmitted when a mating connector is removed and automatically open when the mating connector is inserted.
2. Description of the Prior Art
FIG. 1, labeled xe2x80x9cPrior Art,xe2x80x9d shows a typical fiber-optic connector C with a ferrule F, having centrally-located optical fiber (or fibers) O terminating at its surface, extending from the end of a connector body B1. Outer body B2 slides over connector body B1. It is well known that damage to the end of the optical fiber O itself (dirt or scratches) can also cause severe scattering of the light beam emitted from the optical fiber O and insertion loss, potentially rendering the connector C inoperative.
Since the light used in fiber optic communications is generated by lasers, the light can potentially cause damage to the eyes. The recent trend toward more powerful signal lasers has made fiber optics more dangerous than they were previously. Thus, a number of patents disclose fiber-optic adapters with spring-loaded shutters that are pushed inward by the insertion of a male connector to prevent light emissions from the adapter. U.S. Pat. No. 6,004,043 to Abendschein et al., for example, discloses a spring-loaded shutter door that is disposed at an angle xcex8 inwardly into the receptacle and is pushed out of the way by the inserted male connector (Col. 3, lines 50-54). The inserted male connector contacts the shutter near the sping-loaded hinge, which requires a greater force than if the connector contacted the shutter at a distance from the spring-loaded hinge.
U.S. Pat. No. 6,142,676 to Lu discloses an internal beam stop door. The door is biased by a spring and limited by stop posts (Col. 4, lines 6-21). The door is angled at about 20xc2x0 off the transverse. As seen in FIGS. 23-27, the door is first pushed inward by a cover and then by a prong (FIG. 24). Once the door is held up out of the way, continued insertion operates a cam mechanism that raises the cover (FIG. 26) so that it comes to rest against the raised door (FIG. 27).
It is noted in Lu that slanting the shutter does not actually increase the leverage and does nothing to solve the leverage problem discussed above, as long as the engagement is laterally near to the hinge. This is because the torque required to open the shutter is the product of the force and the distance from the line of the force to the hinge. The line of force extends parallel to the motion of the male connector.
U.S. Pat. No. 6,108,482 to Roth discloses as one of its objects the prevention of damage to the tip of a male optical-fiber connector (Col. 1, line 61, to Col. 2, line 6). Roth shows a spring-loaded shutter in which the shutter surface is divided into a recessed area and a surrounding ledge having a raised surface (Col. 3, lines 47-49 and lines 59-61). The male connector that pushes open the shutter has a projecting optical fiber ferrule with a xe2x80x9cfront mating facexe2x80x9d that xe2x80x9cengages outer surface of shutter and automatically opens the shutterxe2x80x9d (Col. 4, lines 11-14). The shutter""s recess is intended to protect the central area of the mating face, where the fiber termination is located: xe2x80x9cRecessed area has a depth such that the polished ends of the optical fibers are protectedxe2x80x9d (Col. 4, line 17). The fiber termination, but not the ferrule itself, is protected.
The structure disclosed in Roth has several disadvantages. When the ferrule hits the shutter it is subjected to forces that would better be taken by the shoulder of the connector body surrounding it. Roth actually teaches against opening the shutter by pushing it with anything except for the ferrule, stating that the recess xe2x80x9cshould be designed with a depth slightly less than the distance the ferrule projects from the fiber optic connectorxe2x80x9d (Col. 3, lines 53-55; Col. 2, lines 32-34).
The above-cited hinged or spring-loaded shutters also have the disadvantage that they require additional manufacturing steps to insert both the shutter and the hinges and/or springs associated with the shutter. In addition, if the hinges or springs fail, the shutter will become inoperative within the adapter because the shutter will fail to automatically return to the light blocking position. Non-spring loaded shutters, like those mounted in a cantilevered manner, would potentially eliminate this problem.
U.S. Pat. No. 5,104,242 to Ishikawa, for example, discloses a flexible, light-impermeable shutter that covers the optical path of light from a fiber optic source by blocking a portion of the insertion passage inside the adapter. It is connected near the opening of the passage in a cantilevered manner as best seen in FIGS. 1 and 3. Although the shutter is curved so that the sensitive tip of the ferrule does not contact the spring, the ferrule housing contacts the spring during insertion of the connector, as shown in FIG. 3. In Ishikawa, the shutter is located interiorly of the ferrule insertion hole (FIG. 1), which is separate from the insertion passage for the connector body.
U.S. Pat. No. 5,570,445 to Chou et al. discloses a hinged (FIG. 1A) or optionally xe2x80x9cresilient tonguexe2x80x9d (Col. 8, lines 1-5) light-blocking shutter disposed within a fiber optic adapter. The shutter is attached to the inner surface of the housing of the adapter. Given the configuration of the connector, the ferrule tip (FIG. 2C) contacts the shutter directly when the connector is inserted into the adapter.
U.S. Pat. No. 5,708,745 to Yamaji et al. discloses a pair of mating optical shields formed over the opening of an adaptor insertion passage (FIG. 1) and connected to the opening of the adapter in a cantilevered manner with a spring bias that disposes the shields in a closed position to prevent optical emissions.
U.S. Pat. No. 6,302,592 to Zxc3xcllig discloses as the prior art, an interiorly disposed, hinged shutter for use with fiber optic adapters for preventing emissions of light (citing U.S. Pat. No. 5,363,460 to Marazzi et al.). Specifically, Zxc3xcllig shows a spring-loaded, hinged xe2x80x9cradiation protectionxe2x80x9d shutter attached to the housing of the adaptor and forming a cantilever (FIG. 1). A leaf-spring is attached to the lower portion of the shutter to hold the shutter in a light-blocking position when there is no male connector situated in the insertion passage of the adapter (FIG. 1).
In view of the foregoing, it should be apparent that there still exists a need for an apparatus for blocking light emissions from a fiber optic connector in an open adapter using a cantilevered shutter that does not require a hinge or spring, that is designed to swing open by a force exerted far from the connection point, and that uses a simple, inexpensive, and foolproof shape that ensures that the delicate tip of the inserted connector does not contact the shutter, risking damage.
It is, therefore, an object of the invention to provide a fiber optic adapter that has a light-blocking shutter inside the insertion passage of the adapter that prevents light emissions from a fiber optic cable connected to one end of the adapter from causing eye injury.
It is another object of the invention to provide a fiber optic adapter that has a shutter that is attached to the adapter in a cantilevered manner.
It is still another object of the invention to provide a fiber optic adapter that has a shutter made of a material that automatically returns the shutter into a light-blocking position inside the adapter when a male connector is removed from the adapter.
It is another object of the invention to provide a fiber optic adapter that has a light-blocking shutter that does not require a hinge or spring to operate the shutter so as to simplify the manufacturing process and enhance the reliability of the shutter.
Briefly described, these and other objects of the invention are accomplished in accordance with its apparatus aspects by providing a female or receptacle connector or adapter with a passage having a light-blocking shutter that is connected to the adapter in a cantilevered manner. The adapter passage may accept mating male connector or plug, such as for example the SC connector shown in FIG. 1, in such a way that the fiber optic end O is aligned with and juxtaposed to another fiber end very precisely, so that light is transferred into (or from) the fiber end O. The adapter holds the other fiber. When that other fiber is active, light is emitted from its terminus and will shine out of the passage when the male connector is not inserted in the adapter passage. Single and multiple-housing adapters holding two connectors in opposite relationship to each other (i.e., a bi-directional adapter), and adapters holding more than two connectors in opposite relationship to each other, are contemplated.
The invention provides a shutter on one side (or both sides) of the adapter passage to block the light emissions from the optical fibers. It is pushed out of the way by the male connector (e.g., that of FIG. 1) when the male connector is inserted. The shutter is cantilevered so as to remain in a light-blocking position until pushed open, and to automatically spring back when the male connector is withdrawn due to the material used to make the shutter. Preferably, the shutter is made by die-cast or cutting and stamping a metallic sheet. It may also be made by other common metal working processes. The shutter may also be made of plastic or a metallic-coated plastic as long as there is nearly zero-percent light transmission (i.e., about 100-percent opacity) through the shutter. Any suitable materials and manufactures are within the scope of the invention.
The shutter includes a light-blocking panel portion, a bumper panel portion and a base plate portion. In the first embodiment of the shutter, the bumper panel is the first part to contact the male connector when the male connector is inserted in the insertion passage, and is placed so that only the shoulder of the body of the male connector, and not the ferrule or optical end, touches it. By taking all of the insertion force, the bumper panel protects the delicate extending tip of the male connector (e.g., the ferrule F of FIG. 1). The fastening portion includes two C-shaped ends on either side of the shutter for snap-fitting onto a coupling sleeve inserted into the adapter.
In the second embodiment of the shutter, the bumper panel includes a dimple protruding above the surface of the bumper panel. The dimple is the first part to contact the male connector in the same manner as described above. The fastening portion of the shutter of the second embodiment includes a circular hole through the base plate for receiving a rivet, pin, screw or other device for attaching the shutter to the adapter.
To further protect the ferrule, the leading edge of the bumper (the edge foremost in the longitudinal direction, that first contacts the inserted connector body) is preferably set back from the front surface of the adapter body by a longitudinal-depth distance greater than the bumper height (and therefore also greater than the longitudinal ferrule extension d). When this set-back is greater than d, the tip of the ferrule F will not touch the leading edge of the shoulder if the connector is inserted off-center. The setback or longitudinal-depth distance not only helps to prevent ferrule contact, it also makes it more difficult to open the shutter with a finger, pencil, or the like because the bumper is recessed into the adapter body.
It is preferred that in the transverse direction (the direction perpendicular to the longitudinal or insertion direction), the bumper panel height be greater than the distance between the center of the ferrule F tip and the edge of the shoulder of the ferrule body (FIG. 1). This ensures that the entire optical path of the optical fiber O is blocked by the bumper panel portion of the shutter.
It is also preferred that in the transverse direction, the separation between the side of the ferrule and the adjacent outside of the connector body exceeds the transverse distance from the side of the adapter body aperture to the top of the bumper; that is, the ferrule is xe2x80x9cabovexe2x80x9d the bumper panel. Such a relationship ensures that when the outside of the male connector body is against the inside of the passage aperture, the ferrule does not touch the bumper.
The connector housing includes a space into which the shutter is substantially recessed when the male connector is fully inserted, thus eliminating any interference with light transmission that the shutter may cause.
The bumper panel increases the mechanical advantage of the male connector in swinging the shutter out of the way. Besides extending along the insertion axis to protect the connector tip, the bumper panel also extends away from the hinge line in a direction that is transverse to the insertion direction, i.e., toward the middle of the insertion passage. This increases the torque acting on the shutter relative to the hinge line, and makes for faster and easier shutter opening and decreased force on the shutter hinges as the male connector is advanced into the insertion passage.